Kila on Nostr: Any #FountainPen folks know why several of my pens write darker at first on every ...

Any #FountainPen folks know why several of my pens write darker at first on every use, then lighten to the ink’s “normal” color? See photo for example. This ink is meant to be pink. The pen is a piston filler, and this is the only color I’ve ever put in it. I’ve used up about 2/3 of the first fill.